1. Field of the Invention
The present invention relates to a speaker for use in a television receiver and in various audio/video apparatus.
2. Description of the Prior Art
In most of television receivers, a speaker is located at both sides of a cathode ray tube. Speakers of an oblong profile, such as square, oval, etc. have been used for the application. Recently, an increasing number of cathode ray tubes are assuming the screen dimensions of a laterally expanded aspect ratio. As a result, the speakers are requested to have a narrower profile. The speakers are also requested to be able to reproduce high-quality sound corresponding to an improved picture quality.
A conventional oblong speaker is described next with reference to FIG. 6, FIG. 7 and FIG. 8.
FIG. 6 is an exploded perspective view, FIG. 7 is a perspective view of an integral unit consisting of voice coil bobbin unit and a diaphragm unit, and FIG. 8 is a perspective view of a sheet for the integral unit consisting of the voice coil bobbin and the diaphragm before they are formed into the integral unit.
An integral unit 1 consists of a diaphragm unit 1a of an oblong shape having a non-axial symmetry with the major axis and the minor axis for generating the air vibration and a voice coil bobbin unit 1b. The periphery of diaphragm unit 1a is supported by a frame 3 via an edge 2. A supplement cover 9a, 9b is adhered to the diaphragm unit at both ends of the major axis, which are the portions of the diaphragm which are not formed.
A truss 8 is provided bridging the inner circumference of voice coil bobbin unit 1b, and connected to about the middle of a damper 7 having an approximate shape of a letter xe2x80x9cSxe2x80x9d, so that the voice coil bobbin unit is supported by the frame 3 in a freely vibrating manner.
The frame 3 is provided in the middle hollow part with a plurality of magnetic circuits 6 formed of a yoke 4 and a magnet 5. A coil 1c is attached firmly around the voice coil bobbin unit 1b, and the coil 1c is placed in the gap of magnetic circuit 6. The voice coil bobbin unit 1b makes a piston motion in accordance with a drive current supplied to the coil 1c. Thus the diaphragm unit 1a vibrates to radiate sound waves.
A gasket 3a is provided to fix the edge 2 on the frame 3.
The integral unit 1 consisting of the voice coil bobbin and the diaphragm is prepared by first producing the diaphragm unit 1a and the voice coil bobbin unit 1b out of an oblong sheet 1d of hard aluminum, paper, resin film, or the like materials, as shown in FIG. 8, by forming it into the shape of an inverse letter xe2x80x9cUxe2x80x9d, and then winding a magnet wire around it using a winding jig for forming the coil 1c. The conventional integral unit 1 consisting of the voice coil bobbin and the diaphragm thus prepared, however, bears with it the drawbacks as described below.
1. The conventional integral unit is provided by forming an oblong sheet into the shape of an inverse letter xe2x80x9cUxe2x80x9d to produce the voice coil bobbin unit 1b and the diaphragm unit 1a, and then the coil 1c is wound around it. As a result, the voice coil in the semi-circular portions at both ends of the major axis is formed with the coil 1c alone. Therefore, the rigidity is not high enough, and the coil 1c easily gets loosened.
2. The conventional integral unit 1 consisting of the voice coil bobbin and the diaphragm is provided by forming an oblong sheet into the shape of an inverse letter xe2x80x9cUxe2x80x9d, and winding the coil 1c around it, and then a diaphragm supplement cover 9a, 9b made of paper, resin or other such material that is suitable for manufacturing the diaphragm formed into a semi-spherical shape is attached with adhesives in advance or during the assembly process on the diaphragm at both ends of the major axis, or the places void of the diaphragm. This not only lowers productivity of the manufacturing, but the added weight due to the supplement covers 9a, 9b and the adhesives deteriorates the level of sound pressure.
The present invention addresses the above described drawbacks, and aims to provide a speaker that has an improved sound quality and performance at a reduced cost of assembly. A speaker of the present invention comprises a magnetic circuit containing at least the magnetic gap, a frame connected to the magnetic circuit, and an integral unit consisting of a voice coil bobbin unit and a diaphragm unit connected at the periphery of the frame via an edge. The integral unit is formed of a ring shape voice coil bobbin unit which is wound around with coil to be placed in the magnetic gap and a diaphragm unit formed in the shape of an inverse letter xe2x80x9cUxe2x80x9d which is disposed on the upper edge of the voice coil bobbin unit. Since the voice coil bobbin unit is formed to a ring shape in the above described configuration, the rigidity is enhanced. This prevents an irregular winding of a coil on the voice coil bobbin, and the coil does not get loosened easily.